1. Field of the Invention
The present invention relates to a device such as a digital VCR for the PAL system for digitally recording and reproducing PAL signals on a recording medium, such as a magnetic tape.
2. Description of the Prior Art
As prior art pertinent to the present invention, Japanese Laid-Open (Unexamined) Patent 60-220694 discloses the high speed reproduction of color signals in a digital VCR is disclosed. An explanation thereof follows.
In a digital VCR, digital composite signals to be recorded are numbered by the same address in each field and recorded in a recording circuit system, on the other hand, there is provided a memory in a reproduction system, so that the reproduced digital composite signals are written in the memory with the address assigned thereto, and after a given amount of the composite digital signals are written in the memory, the written signals are read out to reproduce the picture image. The start address of each address to be attached to each field of the digital composite signals to be recorded is attached to the same specific line signals in every video frame, specifically, as to the first field and the second field in one video frame, each address is attached to the line signals situated on the upper line and lower line in an interlaced relationship. In the NTSC system, since the phase of the chrominance signal is reversed every line and every video frame, the start address is attached to the line signals of the positive phase chrominance signal in the first field and the second field and is attached to the line signals of the negative phase chrominance signal in the third and fourth fields. When the recording tape recorded in the above manner is reproduced at a high speed, the digital composite signals across several fields are written in the memory with irregular phases since the phases of the chrominance signals are different from field to field, even if the address is the same. Accordingly, the hue of the reproduced image signal can not be displayed correctly. Considering this, the prior art, the start addresses are attached to the same phase line signals of the chrominance signals from the first field to the fourth field. For example, the start addresses from the second field to the fourth field are attached to the line signal on the line (in the TV picture face) upper by one line in an interlaced relationship. This means an expansion of the line signals of the consecutive four lines in the vertical direction, if an picture made of 1 frame formed of 525 lines is considered. By the arrangement, the line signal of the chrominance signal on the same line can be written into the same address of the memory, without respect to the field, thereby resulting in the correct hue of the reproduced picture during high speed reproduction.
If described in the prior art system is applied to a PAL signal, recording can be effected by attaching the start addresses to the line signals of the chrominance signals of the same phase from the first field to the eighth field according to the color frames of the eight field sequence and recording them. This means that the line signals to which the start address are attached are expanded across the consecutive eight lines in the vertical direction considered on a 1 frame=625 line basis.
The arrangement mentioned above has two obstacles. One is that the deterioration of the picture quality in the vertical direction in the reproduced picture is large because 8 consecutive lines are dealt with as one identical line during high speed reproduction. Another is that since the region containing the recording lines in which the lines having the start address act as the leading lines moves field to field in the vertical direction by eight lines, dummy lines are formed at the top and bottom portions of the region containing the recording lines. The number of the dummy lines per field is EQU 8/2-1=3 lines
and therefore, the effective line number per field is the result of the subtraction of 3 from the recording line number.